What are lithium-ion batteries?

Lithium-ion batteries are now associated with electric vehicles, but what exactly are they and how do they work?

Last Updated: 10 Oct 2018

Anyone spending time researching or looking at electric vehicles will come across the term lithium-ion battery. Already used in laptops, phones and other electronic devices, they are now commonly used in electric, plug-in and hybrid vehicles as the source of storage for electricity to power the electric motors on board.

They have several advantages over conventional lead acid batteries as they are lighter, more energy dense and come with a longer lifespan.

What is a lithium-ion battery?

A lithium-ion battery is made up of multiple lithium-ion cells. The lithium-ions from these cells move from the negative electrode to the positive during discharge – when you’re driving the vehicle – and back during charge. The whole process is made possible by the electrolyte.

There are several advantages that lithium-ion batteries have over conventional lead-acid or other types of batteries. They’re lighter than most other battery technologies, which makes them ideal for electric vehicles that require a large number of battery cells.

They’re also very energy dense. In comparison, a typical lithium-ion battery can store 150 watt-hours of electricity in a one kilogram battery. A lead-acid battery, like the one found in normal cars that operates the alternator and starter motor can only store 25 watt-hours per kilogram.

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Lithium-ion batteries can also go through a number discharge and charge cycles with only a small deterioration in their performance. What this means is that you can charge and use your electric vehicle hundreds of times before seeing a fall in battery performance. A fall in battery performance would affect the range of the electric vehicle.

It’s important to note that the lithium-ion battery in an electric vehicle isn’t a single unit, but rather is made up of multiple battery cells stacked together. The more cells the higher the capacity of the battery is – measured in kilowatt hours (kWh).

Hybrid batteries are often between five to 10kWh, rising to 10kWh to 20kWh for plug-in vehicles. Electric vehicles can come with anywhere from 20kWh to 100kWh batteries.